Method and device for generating EUV radiation or soft X-rays

Abstract

The present invention relates to a method and device for generating optical radiation, in particular EUV radiation or soft x-rays, by means of an electrically operated discharge. A plasma (15) is ignited in a gaseous medium between at least two electrodes (1, 2), wherein said gaseous medium is produced at least partly from a liquid material (6) which is applied to a surface moving in the discharge space and is at least partially evaporated by one or several pulsed energy beams. In the proposed method and device the pulses (9) of said pulsed energy beams are directed to at least two different lateral locations with respect to a moving direction of said surface. With this measure, the radiation emission volume is expanded, less sensitive to spatial fluctuations and can be adapted better to the requirements of optical systems of any applications. Furthermore, the optical output power can be increased by this measure.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a method and device for generating optical radiation, in particular EUV radiation or soft x-rays, by means of an electrically operated discharge, wherein a plasma is ignited in a gaseous medium between at least two electrodes in a discharge space, said plasma emitting said radiation that is to be generated, and wherein said gaseous medium is produced at least partly from a liquid material which is applied to a surface moving in said discharge space and is at least partially evaporated by one or several pulsed energy beams. Such discharge based light sources emitting EUV radiation or soft x-rays, in particular in the wavelength range between approx. 1 and 20 nm, are mainly required in the field of EUV lithography and metrology.BACKGROUND OF THE INVENTION[0002]In light sources of the above kind the radiation is emitted from a hot plasma produced by a pulsed current. Very powerful EUV radiation generating devices are operated...

AI Technical Summary

Benefits of technology

[0004]It is an object of the present invention to provide a method and device for generating optical radiation, in particular EUV radiation or soft x-rays, by means of an electrically operated discharge, which allow a more effective use of the generated optical radiation on the one hand and achieve a higher output power of the device on the other hand.

[0012]In another embodiment also comprising such a feedback control, an aperture is arranged in the optical path of the generated optical radiation. Several radiation sensors are arranged at the edges or borders of the aperture opening in order to detect radiation not passing through the aperture opening an emission characteristics of said generated optical radiation. The feedback control may then be performed by minimizing the radiation detected by the radiation sensors. At the same time the radiation energy passing through the aperture opening may be measured in order to maximize this radiation. Another possibility for the feedback control is to maximize the optical radiation passing through the aperture opening and to achieve at the same time an approximately equal amount of radiation detected by each of the sensors.

Problems solved by technology

Furthermore, the geometrical form of the EUV or soft x-rays emitting volume normally is not adapted to the optical system using this EUV radiation or soft x-rays, which often comprises circular apertures for guiding the EUV radiation to the reticle and the wafer in case of EUV lithography, for example.

Therefore, in such applications the EUV radiation or soft x-rays may not be used effectively.

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